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# Questions tagged [physical-units]

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1 vote
106 views

### FFTs, Spectrograms, and Units

I am new to signal processing and I have likely a very easy question but I have found inconsistent answers everywhere. When performing an FFT, does it matter what units the amplitude is in? Currently ...
• 11
1k views

### Units of 6.02*N + 1.76 as an FFT noise floor

I'm working on estimating the FFT noise floor for a data acquisition system my colleagues and I are designing. I've read MT-001 several times. In general, I think I get it. However I'm a little stuck ...
• 296
37 views

### How to convert in site spectra to satellite spectra?

I want to convert the in situ reflectance into satellite reflectance using SRF (Spectral response function). I have downloaded the SRF file but I find that the bands wavelengths are different than in ...
1 vote
280 views

### What is the unit of velocity calculated using Savitzky–Golay filter?

I have data from an eye tracker collected while subjects were doing a saccadic task (i.e. fast eyes movements). Specifically, I have the position (in degree) on the x and y axes, collected at 120Hz. ...
• 11
123 views

### Creating the frequency-spectrum with VC-curves for Building Vibrations measurement

I'm very new to signal processing and can't get ahead: I'm using an Accelerometer to measure the acceleration of i.e. the building vibrations or elements/machinery etc. For creating the spectrum, I ...
1 vote
1k views

### Fourier Transforms, Convolution, Cross-correlation: what is their physical unit exactly?

Let us assume we are talking about real, deterministic, electrical signals $x(t)$ and $y(t)$ (magnitude in Volts). There are different kind of Fourier Transforms. I made a table to summarize: NB: By ...
621 views

### Making the units of a analytically calculated PSD consistent with the units of an FFT

One thing that has always puzzled me is making the units of an analytically derived Power Spectrum Density (PSD) consistent with the units of an FFT. Let's say we record the output of a frequency ...
• 199
1 vote
67 views

### Changing units in Fourier filtering

I'm applying a radial low-pass filter on a $H{\times}W$ pixel 2D image $I$ where $H \neq W$. To implement this filter, I apply 2D DFT to $I$ to produce $I'$, the $H{\times}W$ frequency domain ...
• 165
43 views

### Loss of precision due to low-pass filtering in physical units

Suppose I have a $10{\times}10$ pixel image, where each pixel represents 1 mm in physical units, and I apply a Gaussian low-pass filter with $\sigma = 5$. Can I make any statements such as "the ...
• 165
74 views

### Correct way of viewing negative voltages in units of dB for noise analysis

I have a voltage signal, on top of which there is some noise. I am interested in the noise components so the way I am trying to do this is to fit the known signal to the data and look at the residuals....
• 199
1k views

• 113
160 views

### Normalizing Cepstrum by Energy

I have separately computed the cepstrum and the energy of a finite discrete-time signal. If the energy of the signal is high, we would expect (on average) larger cepstral values than if the energy of ...
• 185